Involvement of the mitochondrial permeability transition pore in chronic ethanol-mediated liver injury in mice

Abstract

Chronic ethanol consumption increases sensitivity of the mitochondrial permeability transition (MPT) pore induction in liver. Ca2+ promotes MPT pore opening, and genetic ablation of cyclophilin D (CypD) increases the Ca2+ threshold for the MPT. We used wild-type (WT) and CypD-null (CypD−/−) mice fed a control or an ethanol-containing diet to investigate the role of the MPT in ethanol-mediated liver injury. Ca2+-mediated induction of the MPT and mitochondrial respiration were measured in isolated liver mitochondria. Steatosis was present in WT and CypD−/− mice fed ethanol and accompanied by increased terminal deoxynucleotidyl transferase dUTP-mediated nick-end label-positive nuclei. Autophagy was increased in ethanol-fed WT mice compared with ethanol-fed CypD−/− mice, as reflected by an increase in the ratio of microtubule protein 1 light chain 3B II to microtubule protein 1 light chain 3B I. Higher levels of p62 were measured in CypD−/− than WT mice. Ethanol decreased mitochondrial respiratory control ratios and select complex activities in WT and CypD−/− mice. Ethanol also increased CypD protein in liver of WT mice. Mitochondria from control- and ethanol-fed WT mice were more sensitive to Ca2+-mediated MPT pore induction than mitochondria from their CypD−/− counterparts. Mitochondria from ethanol-fed CypD−/− mice were also more sensitive to Ca2+-induced swelling than mitochondria from control-fed CypD−/− mice but were less sensitive than mitochondria from ethanol-fed WT mice. In summary, CypD deficiency was associated with impaired autophagy and did not prevent ethanol-mediated steatosis. Furthermore, increased MPT sensitivity was observed in mitochondria from ethanol-fed WT and CypD−/− mice. We conclude that chronic ethanol consumption likely lowers the threshold for CypD-regulated and -independent characteristics of the ethanol-mediated MPT pore in liver mitochondria.